Tic-Tac-Toe rules
The goal
Get three of your marks, X or O, in a row before your opponent does. The row can be horizontal, vertical or diagonal. The first player to make three in a row wins; if all nine squares are filled and nobody has, the game is a draw.
Setting up
- The board
- A three-by-three grid: nine squares in all.
- The players
- Two players. One plays X and the other O. X traditionally goes first.
How to play
Taking turns
Players take turns placing one mark in an empty square. Once a mark is placed it can’t be moved or removed. Play continues until someone wins or every square is filled.
Winning
You win by getting three of your marks in a line:
- Horizontal: across any row.
- Vertical: down any column.
- Diagonal: corner to corner through the center.
A draw, or cat’s game
If all nine squares are filled and neither player has three in a row, the game is a draw, sometimes called a “cat’s game”. With perfect play from both sides, Tic-Tac-Toe always ends in a draw.
On this site
Play the computer on Easy or Unbeatable, pass one device back and forth with a friend, or invite a friend online with a link. X always moves first, and in a rematch the other player starts. Unbeatable plays perfectly, so a draw is the best you can do against it.
Strategy tips
- The center is strongest
- It is part of four winning lines, more than any other square.
- Corners come next
- Each corner is part of three winning lines.
- Make two threats at once
- Set up two ways to win at the same time. Your opponent can only block one.
- Block your opponent
- Every turn, check whether they have two in a row. If they do, and you can’t win right now, block them.
Perfect play
Tic-Tac-Toe is a solved game: there is a known strategy that guarantees at least a draw.
- If you go first: play the center or a corner to give yourself the best winning chances.
- If you go second: take the center if it’s free; otherwise take a corner.
- Always block: if your opponent has two in a row, you must block them.
- Create forks: set up positions where you have two ways to win.
- Block your opponent’s forks: don’t let them reach a position with two ways to win.
Common mistakes
- Taking an edge square with your first move. The center and the corners are stronger.
- Missing an obvious threat from your opponent.
- Not noticing that your opponent is setting up a fork.
- Blocking when you have a winning move available. Take the win.
Ready to play?
Play the computer on Easy or Unbeatable, or invite a friend.